Rex Tenebrae
by DeanWinchesterPercyJackson
Summary: In the future, Percy is King of everything! Athena, bravely risks her life, by traveling 500 years in the past to warn the gods of the darkness which will consume Percy if they go through with their plan to send him to Tartarus. But danger lurks everywhere. King Percy from the future travels after Athena, intent on saving his life, and his throne.
1. Chapter 1

"Ah!" Polybotes said, smiling widely as he stood, and turned at the sound of the throne room doors being pushed open. "After 150 years, the King has awakened at last!"

The King grinned darkly as he strode towards Polybotes, black cape billowing behind him. He spoke.

"One hundred and fifty years. My how time flies when you're trapped in suspended animation."

The King made his way over to his throne, seating himself upon the black object as he went on. "What of my Queen, Polybotes, is she still locked in suspended animation?"

Polybotes bowed when his King addressed him.

"She awoke about fifty years ago Lord."

The King sighed.

"Go retrieve her. I'm sure she's missed me?"

Polybotes bowed again, turning as he spoke.

"Immensely my Lord."

The King smiled, but as soon as Polybotes had closed the door behind him, the smile had dropped to a glare. The King quickly lifted himself from his throne, striding quickly over to the window, staring down at what had once been New York, from the top floor of the building that had once been the Empire State building. The King sighed. He closed his eyes, as image after image flashed through his mind of long ago when he was considered sane.

 **Below! Spoilers for Lightning Thief, and Son of Neptune through Blood of Olympus**

 _Percy raised his sword. He hurled himself at the giant, but Polybotes swept his hand through the water, leaving an arc of black oily poison. Percy charged straight into it, faster than Jason could yell 'Dude, what are you thinking?' Percy dropped Riptide. He gasped, clawing at his throat. The giant threw his weighted net and Percy collapsed to the floor, hopelessly entangled as the poison thickened around him._ **1)**

' _A slow death!' She screamed. 'A death from a thousand poisons!'_

 _All around her, poisonous green plants grew and burst like overfilled balloons. Green and white sap trickled out, collecting into pools and began flowing across the ground toward Percy. The sweet smelling fumes made his head feel wobbly._

' _Percy!' Annabeth's voice sounded far away 'Uh, hey, Miss Wonderful! Cheerful! Grins! Over here!'_

 _But the goddess of misery was now fixated on Percy. He tried to retreat again. Unfortunately, the poison ichor was flowing all around him now, making the ground steam and the air burn. Percy found himself stuck on an island of dust not much bigger than a shield. A few yards away his backpack smoked and dissolved into a puddle of goo. Percy had nowhere to go._ **2)**

' _Just listen okay?' Piper took a deep breath. Everybody listen.'_

 _Piper met their eyes, one person at a time._

' _Eidolons,' she said, using her charmspeak, 'raise your hands.'_

 _There was a tense silence._

 _Leo laughed nervously. 'Did you really think that was going to-?'_

 _His voice died. His face went slack. He raised his hand. Jason and Percy did the same. Their eyes had turned glassy and gold. Hazel caught her breath. Next to Leo, Frank scrambled out of his chair and put his back against the wall._

' _Oh gods.' Annabeth looked at Piper imploringly. 'Can you cure them?'_

 _Piper wanted to whimper and hide under the table, but she had to help Jason. She couldn't believe she'd held hands with...No, she refused to think about it._

 _She focused on Leo since he was the least intimidating._

' _Are there more of you on this ship?' She asked_

' _No.' Leo said in a hollow voice. 'The Earth Mother sent three. The strongest, the best. We will live again.'_

' _Not here you won't,' Piper growled. 'All three of you listen carefully.'_

 _Jason and Percy turned toward her. Those gold eyes were unnerving, but seeing all three boys like that fueled Pipers anger._

' _You will leave these bodies' She commanded_

' _No.' Percy said_ **3)**

 _Hazel, Frank and Percy were left alone in the dark, staring across the road at the close up convenience store._

' _Well that was different.' Frank muttered._

 _Percy shuddered violently. Hazel knew he needed help, or rest, or something. Seeing that army seemed to have triggered some kind of memory, leaving him shell shocked. They should get him back to the boat_ **4)**

 _The last thing I remember is collapsing on a wooden porch, looking up at a ceiling fan circling around me, moths flying around a yellow light, and the stern faces of a familiar looking bearded man and a pretty girl, her blond hair curled like a princess's. they both looked down at me and the girl said_

' _He's the one. He must be.'_

 _Silence Annabeth.' the man said. 'He's still conscious. Bring him inside.'_ **5)**

Percy turned, his smile back in place as his wife, his true love, his Queen, Annabeth walked in, her long, black dress moving softly around her elegant and slim form as she hurried quickly over to him. The two embraced. When they pulled apart, Annabeth set a hand on Percy's cheek as she asked

"What were you thinking about?"

Percy smiled at her lovingly, his arms wrapped around her waist as he leaned into her touched.

"Old friends. New enemies."

Annabeth sighed, leaning into Percy's chest, her hand still on his cheek. They stood in silence like that, before Percy voiced the pressing matter that had been on his mind since he'd awoken.

"What of the remaining Olympians? I trust you destroyed them?"

Annabeth sighed, wrapping her arms around Percy's neck, intertwining her fingers in his hair as she answered.

"I...I wanted to Percy. I swear I did! But...but I was too scared. Too weak! Every Time I'd make my way to where the gods live in hiding, I'd freeze up, remembering the battle that went down between you and Poseidon before I was forced to put you in suspended animation just to save your life. But…" she sighed, pulling her face out of Percy's neck, to look him in his blood red eyes as she went on. "but you're here now, so those….those... _monsters,_ those self proclaimed _god's_ will finally fall! R-right Percy? You _do_ want revenge after what they did to you?"

Percy sighed, tightening his hold on Annabeth just slightly.

"Yes. Believe me Annabeth, I swear on the Pit they will pay. But I may need a bit of combat training with Polybotes and Oceanus first. After all, I've been out of practice for a century and a half!"

Annabeth nodded, trying to hide her disappointment as Percy ended their embrace. He always ended all physical contact quickly.

"Would you like me to call in Polybotes?"

Percy sighed, eyes barely open as he thought. After a moment, he opened his eyes fully, and shook his head.

"Not yet. Are all our prisoners still down there?"

Annabeth sighed, straightening the skirt of her dress as she answered.

"All but one yes."

Percy frowned, eyes slightly glowing white, which showed only a portion of his power. He began breathing heavily, the monster inside, more in control at that moment than Percy, fueled by rage as he advanced on Annabeth. He froze, his hand inches away from grabbing her throat. The blazing white died, and the red returned. Percy visibly took a deep breath before speaking through clenched teeth.

"Who. Escaped?"

Annabeth looked away, her hands bunched into fists around a portion of her dress. She took a deep breath.

"Athena. But, I don't think she was going back to the gods. Not these gods anyway."

Percy looked at Annabeth, confusion written in the lines of her face.

"What do you mean 'not these gods'?"

Annabeth sighed, releasing the fabric of her dress, quickly smoothing it as she answered

"I think she's going to the past. To try and convince the Olympians of before to not send you to Tartarus."

Percy's eyes went wide, and he yelled out

"NO! She _can't_ do that! If the gods don't send me to Tartarus, then this future never happens! We have to stop her!"

Annabeth nodded.

"Of course. I'll the most powerful of your army immediately."

Annabeth turned, and quickly headed for the throne room doors, but Percy's dark tone stopped her."

"No." Annabeth flinched, turning around, a questioning look in her eyes. Percy went on. "This is too drastic a measure to task Hyperion with. No, this will require me to step up. _I_ will be the one to go back in time and stop Athena."

Annabeth bit her lip.

"But you've only just woken up, surely-"

Percy cut her off sharply.

"No. Get Kronos. I leave immediately."

Annabeth nodded.

"Of course. To what time should I tell him send you?"

Percy stood tall as he answered

"Five hundred years ago. New York City."

 **Hey! I own nothing! (Forgot to say) All credit goes to the awesome Rick Riordan. Here's the other credit for his books**

 **Blood of Olympus- Page 264**

 **House of Hades- Page 361**

 **Mark Athena- Page 146**

 **Son of Neptune- Page 231**

 **Lightning Thief- Page 56**


	2. Athena landsthe King follows

**Here's the next chapter! Hope you like. Also, reviews make me giddy.**

 **Athena POV**

Athena gasped, as her feet touched down, and she collapsed, panting for air. She looked around, trying in vain to ensure she'd landed in the right spot. She hadn't. She groaned, as she slowly, and painfully picked herself up, and limped her way over to the nearest mortal she saw. It was hot, wherever she was. That didn't bother her. What bothered her was, with being the goddess of wisdom, she couldn't tell where she was. She sighed in relief, as she set herself down on a bench, the mortal next to her glancing over, before going back to his book. Athena took a few seconds to catch her breath, before turning to the mortal.

"Hello there."

The man put his bookmarker in his spot, closing the cover, before turning to face the exhausted goddess. He smiled.

"Hello. May I help you?"

Athena swallowed back an odd gag reflex as the man's eyes met hers, and smiled as she asked

"Would you be able to tell me where I am?"

The man's grin, if at all possible, became larger.

"You're in Australia. I'm just a tourist so I can't show you around if that was your next question."

Athena shook her head.

"No actually. My next question was what's the date in America?"

The man looked at Athena as though she was crazy, before answering

"June third, 2012."

Athena's eyes went wide, before she nodded, standing and making her way somewhere else. As soon as she was out of sight of the man, she sighed.

"I overshot! How could I! I was aiming for the day the gods sent Perseus to Tartarus. Which was August eighteenth, 2012. But, instead, in my haste to get away from 'King' Perseus's dungeon, I overshot thirteen weeks! It doesn't matter! My only goal now, is to find a way to get to America and fast. If Perseus is smart, he'll follow me and try to stop me by any means necessary. He'll do anything to stop me from changing his fate." Athena shivered as she murmured "Even murder."

THREE DAYS LATER

Athena quickly rushed through Olympus, shocking everyone who saw her. She quickly barged through the throne room doors causing everyone, even her past self, to look up. Their mouths fell open, but before they could speak, Athena from the future was talking.

"I don't have much time. Listen carefully. Apollo, when I'm done, confirm if I'm telling the truth. Now, I'm Athena, but I'm from 500 years in the future, where Perseus Jackson rules as King, with an iron fist. The people who sent him on this path are the ones watching me from their thrones. On the date of August eighteenth, 2012, the gods made...or make...a decision, though why I don't know, to through Percy into Tartarus. He becomes enraged, and later destroys us. Where I come from, Apollo, Artemis, and Poseidon are dead by Percy's hands. Now, he's smart. By now, if he's awake, he'll have noticed I'm missing and likely come after me. He knows it's the only way he can be sure his life and throne remain his. Apollo, am I telling the truth?"

Everyone looked over at Apollo, who nodded, open mouthed. With this piece of confirmation, Athena went on.

"Good. Poseidon, I want you to get Annabeth, and inform her of what has occurred. I want you and her to go down, and protect Perseus's mother, Sally Jackson. Can you do that?"

Poseidon nodded, before flashing out to retrieve the goddesses daughter. Athena nodded, and then, after all the strain, lost consciousness.

….POV CHANGE ATHENA-KING PERSEUS…

Percy cried out, as he landed. He looked around, vaguely dizzy and disoriented. He was on a back road, that much he could tell, but where he wasn't sure. He stood slowly, looking around, trying to determine his position. Before he knew what was happening, he was on the ground once more, a screeching sound ringing in his ears, and a terrible pain burning on his side. He heard a woman's voice proclaim,

"Oh my god! I hit him! Call 911!"

Percy's eyes narrowed, and he made a low growl in his throat at the sound next voice.

"Sally I think maybe you should keep away from him. Just to be safe."

Poseidon. Percy barely kept a lid on his temper, as he slowly pulled himself off the ground, laughing lightly, but loud enough for the people behind him to hear.

"Right." He muttered, though by their silence he was sure they could hear him and recognize his voice. "2012. There are cars. Forgot about those. Funny how things slip your mind when you're in Tartarus."

He slowly pulled himself to his feet, before drawing out his sword, and lunging at the woman. He held the blade to her throat as he growled

"Who are you?"

The woman was stuttering, obviously terrified. Percy tipped his head to the right as he asked

"You're mortal aren't you?"

The woman nodded.

"Yes. My name's Sally Blofis."

Percy pulled back, sheathing his sword, and straightening his back as he spoke, turning to find Poseidon and Annabeth, weapons out. He grinned. Judging by the looks on their faces, they knew him. He spoke

"I suppose I should introduce myself. My name is King Perseus Jackson." Sally gasped, but Percy ignored her and went on "I'm from 500 years in the future, where New York and Olympus have-"

"Yes we heard about that!" Poseidon interrupted, his voice shaking. "Why? What did we do to you?"

Percy narrowed his eyes, his sword out once more.

"You sent me to Tartarus. You made me suffer. And so, in turn, I intend to make you suffer. Oh wait!" His laugh was dark, and demonic. "I already did! Now!" He turned to the woman he'd once called his mother. "Sally Blofis. May I stay a night at your place?"

Even though the man standing before her looked like Percy, other than the red eyes, Sally knew that's not who he was anymore. So, bravely, she shook her head.

"No."

Percy narrowed his eyes.

"I advise you do just as I asked Sally Blofis. Because right now, I am this close to hunting down that son of yours and sending him to Tartarus myself. I came back to ensure that event still happens, but if any of you give me a reason to let it slide, and let myself and my whole kingdom be destroyed I'll take it. But you haven't shown me anything yet."

Percy turned, pushing between Annabeth and Poseidon, even though his entire body tingled in rage at being so close to his biological father, and not killing him. Percy froze as Annabeth spoke.

"Why are your eyes red?"

Percy turned, staring at her, before speaking.

"Because the love of my life, my own wife, once made the mistake of calling me _Poseidon!_ This was my way of ensuring that never happened again."

Annabeth nodded, before voicing her fears.

"Who's your wife?"

Percy smiled, a genuine smile he saved only for Annabeth.

"She is Queen Annabeth Chase. Ex-daughter of Athena, Queen of Ex-New York and Tartarus. Now, if you excuse me, I have a boy by the name of Perseus Jackson to find and destroy!"

…..ON OLYMPUS…

All gods, save for Poseidon, and Athena from the future and Apollo sat, trapped in a heated arguement. All demigods but Annabeth were present as well, this including past Percy. The gods fought over what to do with this new perceived threat of King Percy. Ares choice was simple but stupid.

"Throw him into Tartarus!"

Before the gods could chastise him, a dark laugh echoed all around, emanating from the doorway.

"Now now dear God of War. What would that solve?" All demigods and gods turned toward the voice. Past Percy stared in shock, as King Percy, dressed all in black strode forward. King Percy sighed, continuing. "I mean, come now Ares! I love Tartarus. It's like a second home to me. So I ask, what good would that do? If anything, it would make me stronger."

Past Athena spoke up.

"We could lock him in the prison here on Olympus couldn't we? I mean, it's virtually inescapable! We could keep six chains on each arm and leg, two of which can only be opened by one god."

The surrounding immortals clearly didn't get it, because Athena sighed and went on. "Like, Zeus can unlock one chain on his arm and leg, and Artemis can unlock one on his arm and leg and so on. Does that make sense?"

The gods nodded. They then looked over at King Percy, who stood, arms extended, grin plastered on his face. Zeus quickly lost his patience.

"And you're grinning because?"

King Percy shrugged.

"This is actually a pretty good plan. Plus, if you never send Percy over there to Tartarus, then my world, and my life rapidly falls apart, and I cease to exist. That _was_ your plan in the long run. Right Zeus?"

Zeus nodded quickly.

"Yeah! Yeah of course! Uh, take him away!"

Hermes and Hades nodded, and quickly dragged King Percy off to his cell.

All the way there, King Percy continued to grin.

The Gods had no idea of his true strength.

They had no idea of his true plan, which they had just inadvertently set into action.

 **Hope you liked. From now on, I'll call Percy from the future 'King Percy' and the other Percy either Percy or past Percy. Actually, I'll leave it up to you. Which is easier to remember? Past Percy or Percy? I think Past Percy would be best because when King Percy goes back to his time I'll just call him Percy. What do you think? Please review!**


	3. Trapped in Tartarus

**Here we go.**

 _ **Previously on Rex Tenebrae:**_

" _Let's go and visit Tartarus shall we? I hear it's lovely this time of year."_

 _In a flash of red, the two were gone._

 _ **NOW:**_

"You know, I think I like this plan even better than my original!"

King Percy grinned down at his younger self, who stood, chained to a wall in a cell somewhere in Tartarus. King Percy went on. "What sent me down my path was when the gods sent me to Tartarus. But this! This is even better. Instead of the gods sending you to Tartarus, now you'll follow my path when they don't _save_ you from Tartarus."

Past Percy narrowed his eyes, struggling against the chains even though he knew it was pointless. He growled deep in his throat, causing the sadistic future version of himself to laugh darkly.

"And so it begins! Any last words before your sanity slips away entirely Perseus Jackson?"

Past Percy forced himself to take a deep breath and calm down.

"Why are you doing this to me?"

King Percy narrowed his eyes.

"I'm doing this to save myself. If you never get sent to Tartarus, then you never get angry and you never want revenge. Then you never become me and I cease to exist! I'm simply doing this to ensure my reign continues."

Past Percy shook his head.

"You're insane!"

King Percy laughed, putting his arm around past Percy's shoulder.

"No my boy. _We're_ insane!"

Percy shuddered at the words. The King pulled away from him, continuing to speak.

"You know Percy, I'm disappointed. You never bothered to ask where we are!"

Past Percy narrowed his eyes, suddenly suspicious.

"I know where we are. We're in Tartarus. You made that quite clear."

King Percy sighed.

"Yes. That's _where_ we are. But you never asked _when_ we are!"

Past Percy's eyes went wide as he whispered

"No. That's not possible."

King Percy threw back his head and let out a loud, dark, demonic laugh.

"Oh it is my boy! Welcome to five hundred years in the future! Where I rule and three gods have fallen at my hands!"

Past Percy stared, open mouthed at the man before him before he whispered.

"Who?"

King Percy frowned.

"I beg your pardon? Who who?"

Past Percy took a deep breath.

"Which gods have fallen! How?"

King Percy jumped with glee, clapping his hands together like some twisted child.

"Oh it's a lovely story! Well, the first to fall was Apollo. You see, my lovely queen and I decided to lay siege to Olympus. This was before the gods abandoned it you must understand. Well, lovely Annabeth remained in the throne room, fighting off the gods, adn I jumped into the chariot of Artemis with her. Well, Apollo didn't seem too fond of that idea, and so he set after us. Well, I wanted him to attack adn so I kissed Artemis. Apollo, enraged leapt at me, throwing me from his sisters chariot, and together we fell through the sky. I used my special blade, which can kill immortals and I stabbed it into his stomach. But I didn't want him dead yet, so I sent him and Artemis to my castle, where they now lie in suspended animation."

King Percy paused for a breath and past Percy shouted out.

"You're a monster."

King Percy snorted.

"Call me what you like. Anyway, the last to fall, for now, was Poseidon. It was a battle me versus him. In the end, we were both horribly wounded and dying. He had my sword stuck in his chest adn I had his trident through mine. Quickly I trapped him in suspended animation. I could have killed him, but I kept him around for a sort of target practise. But I knew I was dying, and my dear Annabeth was hurt as well. So I set a timer. She would sleep in suspended animation for one hundred years, and I for one hundred and fifty years. And then, I awoke to find Athena had escaped my prison. And here we are! Any questions?"

Past Percy stared in shock, before asking

"Who else is in your prison?"

King Percy pursed his lips, tapping his chin.

"I'm not actually sure anymore. I'll check for you though if you'd like."

King Percy looked away, lost in his own thoughts, before turning back to past Percy.

"Well, I'll leave you to get settled in."

He turned, heading for the cell door. Just before he slammed it shut behind him, he turned back to his prisoner and said

"Have a nice stay."

 **Like? Hate? Please review!**


	4. Authors note

**Help! I have no idea what to do next. Please please give me ideas on either Twitter ( DeanWPercyJ) or in a review/comment thing.**


	5. Sally

**Oh my god I am SO sorry. My excuse is that when I start watching a new show I get obssesed, so that's all I focus on. So, so, so sorry. Here's the next chapter.**

King Percy sighed as he dropped himself roughly into his throne. He was alone in the room, and yet part of him didn't feel alone. He sighed, resting one elbow on the arm of his throne, while he allowed his eyes to wander to light bluish-green room. After a good five minutes, Percy stood, and made his way through the doors, down the stairs, headed for the dungeon. He had a fairly good guess of who his prisoners were, granted none of them had escaped while he'd slept. He grinned as he approached it. There was a loud click and groan as he forced the door open, and descended even farther to the very bottom of his castle where his prisoners were held. He froze before the last cell in the row. For the first time in over 500 years he felt something deep inside he'd never felt before.

Fear.

He quickly brushed it off, and stepped over the threshold to greet his prisoner. He smirked as the lights in the cell flickered on. He smirked down at the person chained to the wall, before he crossed his arms. The prisoner slowly lifted her head. Her body trembled with exhaustion as she whispered

"Percy. Please."

Percy sighed dramatically, as he moved forward to stand over the prisoner in an intimidating manner.

"What have I told you to call me _mother?!_ "

Sally Blofis bit back a sob as she dropped her gaze and whispered

"My King."

Percy smirked, moving away from her.

"Good. You know, you're lucky I let you live. I _was_ planning on having you meet the same fate poor Paul, Hazel, and Piper met. But I felt some sense of sympathy towards you, and so decided to spare you. But the moment you get in my way, the moment you cease to be useful, you're done. Do I make myself clear?"

Sally nodded, knowing the cost if she didn't answer.

"Yes my King."

Percy narrowed his eyes, turning his back on the woman he once called his mother. He stood, frozen and rooted to the spot, before he hung his head.

"Heh. I fear I may be losing my touch. I'm feeling a sense of sympathy for you. Ha!"

With that, King Percy left, slamming the door behind him. He then quickly made his way to the throne room, seating himself down on the steps in front of his throne, sighing.

"What's wrong with me? Seeing my old self….ugh. I'm beginning to feel guilt. I need to do something to get rid of it. But what?"


	6. Final Author's Note

**Author's note**

 **Hey guys! So, I've decided I'm going to remove this story from , and completly rewrite it. The idea will be the same...sort of. Anyway, keep your eyes open for the new version with the same title.**

 **So so sorry! To everyone who liked this story, I hope you read the new version even more!**

 **Thanks!**

 **DeanWinchesterPercyJackson**


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